1. Technical Field
The present invention relates to: a torque detecting device which detects a torque exerted to a rotating body; and an electric power steering apparatus including the torque detecting device and an electric motor for assisting a steering operation.
2. Description of Related Art
A torque detecting device is, for example, described in Patent Document 1. The torque detecting device of the Patent Document 1 includes a magnetic circuit forming member provided on a rotating body having an input shaft and an output shaft which connect to each other via a torsion bar. The device also includes two magnetic flux concentrating rings that concentrate a magnetic flux generated by the magnetic circuit forming member. The two rings locate parallel to each other in an axial direction of the shafts and locate outside an outer circumference of the magnetic circuit forming member, being apart from each other. The device also includes a detecting part that detects a torque, which is exerted to the rotating body, based on a density of the magnetic flux which the rings concentrate.
The above-mentioned torque detecting device is mounted, for example, on an electric power steering apparatus for a vehicle. The electric power steering apparatus includes the rotating body whose input shaft connects to a steering wheel. The apparatus also includes a tubular housing that accommodates the rotating body to support it. The apparatus also includes an electric motor for assisting a steering operation, which connects to the output shaft via a reduction mechanism. The apparatus also includes a controlling part having a microprocessor and coupled to the detecting part and a driving circuit of the electric motor. Based on a torsion arising in the torsion bar, the detecting part detects the torque exerted to the input shaft upon the steering operation of the steering wheel. The electric motor is controlled to be driven based on the detected torque.
In addition, when the torque detecting device is mounted on the housing, the torque detecting device as a whole is inserted into an interior from one end of the housing and is fixed in the interior of the housing.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-149062